Construction of low-tension wire arrays

ABSTRACT

A method of constructing a low-tension wire array including the steps of arraying wires on an expandable frame expanding the wires past their elastic limit, and releasing the frame tension until each wire hangs in catenary. The wires are then placed onto an epoxied sheet and the ends cut.

United States Patent [1 1 3,574,927

l 72] Inventor Albert L. Whetstone [56] References Cited Southport,Conn- UNITED STATES PATENTS 1211 P 794,950 3,049,604 8/1962 Showalter29/597x [45] Patented Apr-13 1971 ms 29/610X [73] Assignee Science k esCorporation 3,091,754 5/ 1963 Nazarre 340/ 173 so 3,206,832 9/1965Strother 29/572 uthport, Conn.

Primary Examiner-John F. Campbell Assistant Examiner-D. C. Reiley [54]CONSTRUCTION OF LOW-TENSION WIRE Attorney-Frank R. Trifari ARRAYS 4Claims, 4 Drawing Figs.

[52] U.S.Cl 29/592, ABSTRACT: A method of constructing a low-tensionwire 29/419, 29/604, 29/610, 29/5271 140/921 array including the stepsof arraying wires on an expandable [51] int. Cl H015 4/00 frameexpanding the wires past their elastic limit, and [50] Field of Search29/(lnquired); releasing the frame tension until each wire hangs incatenary.

29/592, 604, 446; 140/921; 29/419, The wires are then placed onto anepoxied sheet and the ends 460, 527.1, 610 cut.

Patented Apr-i113, 1971 3,514,921

INVENTOR. ALBERT L. WHETSTONE BY ail-wi- KLJkQQL AGENT CONSTRUCTION OFLOW-TENSION WIRE ARRAYS This invention relates to wire arrays andparticularly to a method of constructing a low-tension wire array.

Wire arrays have been employed successfully in digital spark chambers.Such chambers are data acquisition devices which are used to collectdata regarding the nature or movement of high-energy particle or sparkin a gaseous environment. The energy path is through a set of chamberplates which are wire array panels in the particle path. The spark whichwill move through one or more chamber plates, generates a pulse along awire in each chamber plate which is in turn transported to various typesof digital data-recording equipment. Thus, a coordinate picture of themovement of the spark can be obtained.

The chamber plates are commonly constructed of woven wire cloth, thewires alternating with a monofilament acrylic fiber. The cloth issupported by a rigid frame. For purposes of accuracy in readings, it isnecessary to maintain each wire in a tensed condition when finallyassembled. The strength of the frame construction must be sufficient toallow for the tensioning of each wire without any distortion in theplane formed by the frame. With the greater number of wires in largerframes, the distortion in the frame increases because the variation intension along the length of the frame increases.

It is therefore the prime object of this invention to provide a methodof constructing an array of wires with low tension.

It is a further object of the invention to provide a method ofconstructing a wire array with minimal distortion.

It is a still further object of the invention to provide a method ofconstruction for wire arrays which permits the construction of largerscale wire arrays in lower tension, lower distortion frames thanheretofore achievable.

In accordance with the foregoing objects, the inventive method hereinemploys the concept of tensioning each wire in an expandable frame untilthe elastic limit of each wire is exceeded. The tension is then releasedand the wires pennitted to hang in catenary. At this point, each wirewill hang with the same droop, regardless of their original tensionwithin the frame. The wires are then epoxied to a thermoplastic film andthe ends cut.

More specifically, the wires are stretched horizontally on a rack. Theracks are then separated further until the wire exceeds the elasticlimit, which can be defined as the point at which the AL over Lincreases rapidly with tension. The racks are then set closer so thatthe tension is partially removed. The wires then hang in catenary withall tension equal. The wires are now epoxied to a flat plane which ispositioned horizontally under the wires and raised vertically until itcontacts the wires in the center. It is then raised further until thewires are in contact with the plane over the entire length. When theepoxy is cured, the wires are cut loose from the rack upon which theywere positioned. The catenary droop can be set so the wire now exertsnear zero tension upon the plane and thus there is no need to build astrong plane with strong supporting frames. That zero tension resultsmay be understood by considering the case where the catenary has a largedroop and the case where there is high tension and little droop. If thetension is initially low, i.e., large droop, the wire will come undercompression as the plane is raised and so it will not lie straight onthe plane. If the initial tension is too great there will be sometension after the plane is completely raised and the plane will have tobe stronger to resist distortion. Therefore, an intermediate value forthe initial droop exists for which the final tension of the assembledplane is near zero.

The foregoing objects and brief description of the invention will becomemore apparent from the following more detailed description and appendeddrawings, wherein:

FIG. I is a schematic diagram of the employment of chamber platesutilizing wire arrays;

FIG. 2 is a graphical representation of the elastic characteristics of atypical wire;

FIG. 3 shows an expandable frame for tension stretching the wire array;and

FIG. 4 illustrates the catenary suspension after expansion and shows themanner of assembling the wires onto the chamber plate plane.

Referring now to FIG. 1, there is shown a typical chamber plateconstruction in expanded cross-sectional form. A frame mount 10,constructed of any suitable material encases the wire array 11 which isin turn mounted as a plurality of parallel wires on a base of suitablethermoplastic film 12, such as mylar or the like. An energy particle ora spark 13, which can be generated by means of a high voltage across aspark gap, passes through the chamber window area 14 and creates a pulsealong one of the lines 11. Each of the lines I1 are connected, as bysuitable conductors mounted along the edge of the frame I0, to a digitaldata acquisition device 15. By using a plurality of chamber plates inthe path of the particle, and by employing data devices at theinitiation of the spark and at each chamber plate, the movementcharacteristic of the spark can be analyzed.

Clearly the accuracy of the analysis is dependent upon insuring that noextraneous factors enter into the time and position measurement of aspark on a plate. Such factors would include nontensed wires, affectingthe interwire positioning, and varying tensions of the wire, affectingnonplanar distortion of the mounting plate 10. These factors become morepronounced with the size of the plate. A typical construction requiresan active area of approximately 1 meter by 1 meter employing 0.005-inchdiameter copper wire with a linear wire density of 50 lines per inch (50mesh).

To construct the chamber plate with minimal distortion caused bytension, the elastic limit characteristic of the wires are utilized. Asshown in FIG. 2, the elastic limit curve is the relationship between thechange in length to the length, AL over L, as a function of tension, T.As a wire is put under tension, as by stretching, the AL over L willundergo a proportionate increase from point A to point B with arelationship dependent upon the tensile strength of the wire. When theelastic limit, (the tension of point B) is exceeded, relatively slightincreases in tension thereafter produce a disproportionate increase inthe AL over L. When the point C is reached, the wire has reached the endof its expansion range and shows a marked reduction in expansion withfurther tension increases. At some point D after point C, the wire willbreak.

In accordance with this invention, the range of point B to point C isemployed. A wire array 16, with wires positioned in substantiallyparallel relationship, is suspended in a rack such as the expandableframe 17 shown in FIG. 3. The wire ends are attached to the framemembers 18 and 19 respectively. The frame is expandable, as by means m atension screw 20.

The frame members 18 and 19 are preferably each threaded bars which areindependently adjustable and can be employed for laterally adjusting thewire ends with respect to each other to insure that the wires are notonly parallel but that they are orthogonal with respect to the threadedbars.

The tensioning screw 20 serves to expand the frame members 18 and 19 ina direction 21 corresponding to the direction of length of the wires.After the wires have been arrayed along the frame members, the frame isexpanded and the wires stretched until the elastic limit of each wire isexceeded and each wire is in condition defined between the points B andC of FIG. 2. At this point, the tension of the wires is released as byreversing the direction of turn of the tension screw until each wirehangs in catenary with all tension equal. Because each wire is in theB-C range, each wire at this stage will hang with the same dimensionaldroop, regardless of their original tension condition. The actual droopselected will depend on the length of the wire and will represent acompromise value.

To assemble the completed chamber plate, the wires are now bonded as bya suitable epoxy, or similar bonding compound, to a dimensionallystabilized fiat wire support plane 21 (FIG. 4). The support plane 21 ispreferably a sheet of heat-treated epoxy-coated thermoplastic film suchas mylar or the like. The plane 21 is in turn supported on a supportsurface 22 which is coupled to the frame 17 by means of a verticallyadjustable mechanism 23 for imparting vertical motion in the direction24 to the plane 21.

The plane 21 is positioned horizontally under the wires 16 and is raisedvertically untilit contacts the wires in the center 25 of the catenarydroop. It is then raised further until the wires are in contact with theplane over its entire length.

The epoxy is now allowed to cure. When the epoxy is cured, the wires arecut loose from the frame members 18 and 19.

The wires now exert near zero tension on the plane. The near zerotension can be understood by considering the case where the catenary hasa large droop and the case where there is high tension and little droop.If the tension is initially low, i.e. large droop, the wire will comeunder compression as the plane 21 is raised and so it will not bestraight on the plane. If the initial tension is too great there will besome tension left after the plane is completely raised, and the planewill have to be stronger to resist distortion. Thus, an intermediatevalue for the initial droop exists for which the final tension of theassembled plane is near zero.

Subsequent to the positioning and bonding, the wired plane can beassembled as by epoxy bonding to a suitable support frame such as isillustrated in FIG. 1 and connections made to each wire through theframe for subsequent connections to the data acquisition devices.

In this manner, much larger chamber plates can be realized without aconcomitant increase in tension or plane distortion. Planes can thus beconstructed as large as several meters on each side.

Since certain changes and modifications can be readily entered into inthe practice of the present invention without departing substantiallyfrom its intended spirit or scope, it is to be fully understood that allof the foregoing description and specification be interpreted andconstrued as being merely illustrative of the invention and in no senseor manner as being limiting or restrictive thereof excepting as it isset forth and defined in the appended claim.

lclaim:

1. The method of assembling a wire array in a low-tension frameworkcomprising the steps of arranging an array of wires in a substantiallyparallel relationship in an expandable frame with the ends of said wiresaffixed to the frame members, tensioning each wire of said arraysimultaneously by expansion of said frame members in the direction oflength of said wires until the elastic limit of each of said wires ofsaid array is exceeded, removing said tensioning by contracting saidframe members until each of said wires hang in catenary, raising asubstantially flat epoxy-coated planar support surface up into saidarray of wires until the wires contact the surface over its entirelength, allowing said epoxy to cure and cutting said wires loose fromsaid frame.

2. The combination of claim 1 wherein said surface is a sheet ofthermoplastic material.

3. The combination of claim 1 wherein each of said frame members is athreaded bar which is individually adjustable for positioning the wiresrelative to said bar.

4. The method of assembling a wire array in a low-tension frameworkcomprising the steps of arranging an array of wires in a substantiallyparallel relationship in an expandable frame with the ends of said wiresaffixed to the frame members, tensioning each wire of said arraysimultaneously by expansion of said frame members in the direction oflength of said wires until the elastic limit of each of said wires ofsaid array is exceeded, removing said tensioning by contracting saidframe members until each of said wires hang in catenary, raising asubstantially flat epoxy-coated planar support surface up into saidarray of wires until the wires contact the surface over its entirelength, allowing said epoxy to cure, cutting said wires loose from saidframe, and epoxy bonding said resulting wired plane to a support frame.

1. The method of assembling a wire array in a low-tension frameworkcomprising the steps of arranging an array of wires in a substantiallyparallel relationship in an expandable frame with the ends of said wiresaffixed to the frame members, tensioning each wire of said arraysimultaneously by expansion of said frame members in the direction oflength of said wires until the elastic limit of each of said wires ofsaid array is exceeded, removing said tensioning by contracting saidframe members until each of said wires hang in catenary, raising asubstantially flat epoxy-coated planar support surface up into saidarray of wires until the wires contact the surface over its entirelength, allowing said epoxy to cure and cutting said wires loose fromsaid frame.
 2. The combination of claim 1 wherein said surface is asheet of thermoplastic material.
 3. The combination of claim 1 whereineach of said frame members is a threaded bar which is individuallyadjustable for positioning the wires relative to said bar.
 4. The methodof assembling a wire array in a low-tension framework comprising thesteps of arranging an array of wires in a substantially parallelrelationship in an expandable frame with the ends of said wires affixedto the frame members, tensioning each wire of said array simultaneouslyby expansion of said frame members in the direction of length of saidwires until the elastic limit of each of said wires of said array isexceeded, removing said tensioning by contracting said frame membersuntil each of said wires hang in catenary, raising a substantially flatepoxy-coated planar support surface up into said array of wires untilthe wires contact the surface over its entire length, allowing saidepoxy to cure, cutting said wires loose from said frame, and epoxybonding said resulting wired plane to a support frame.